Three hundred fifty seven pedicle screws in 45 patients were tested intraoperatively after radiographic examination revealed acceptable positions. A threshold value equal and below 11 milliAmps was used to identify (Triggered EMG) positive screws. Inspection for evidence of screw to nerve root contact was done.
Results showed eighteen out of 357(5 percent) in 14 out of 45 (31.1 percent) patients were detected by TrEMG. All 18 screws were inspected and exhibited evidence of medial or caudal wall perforation and contact with the adjacent nerve roots.
TrEMG is a real-time intraoperative neurodiagnostic tool that provides an objective basis for reassessment of screw position when there is a discrepancy with radiographic imaging. We believe this technique may afford the surgeon the ability to improve final screw position and thus prevent complications.